Section 19(2) in The Delhi Metro Airport Express Line, General Rules, 2010
(2)Safety Communication.- (i) all communication between Operations Control Center and train operators, section Controller, maintenance staff of electrical, rolling stock, signal and telecommunication and track structures department and other pertaining to movement of trains shall be tape-recorded and preserved for incident analysis and, training, and the mode of preservations and its duration shall be specified in special instructions;(ii)the Delhi Metro Airport Express Line employees shall initiate and acknowledge radio messages in a manner that ensures establishment of communication only between intended parties;(iii)messages affecting train movements shall be addressed by the Traffic Controller to only one train at a time:Provided that in an emergency, a blanket message may be sent by the Traffic Controller to all trains in or approaching a particular area, which must be acknowledged individually by all concerned train operators:Provided further that in an emergency, such message may be given by the Station Controller, if authorised by the Traffic Controller in this behalf.
